1. Field of Invention
This invention relates to an anatomical seat cushion, specifically to such cushions used for orthopedic value.
2. Background
Many people suffer from pain in the rectal and perineal regions of the pelvis. Pain and discomfort stem from a number of causes such as hemorrhoids, rectal surgery or a damaged coccyx. Chronic Pelvic Pain Syndrome (CPPS) can be the source of substantial and prolonged pain. In men, it takes the form of Chronic Prostatitis (CP) and is the source of substantial sensitivity to pressure in the perineum.
In the book A Headache in the Pelvis authors David Wise, Ph.D. and Rodney Anderson M.D. describe the difficulties in living with Chronic Nonbacterial Prostatitis. “In men, chronic pelvic pain (prostatitis) includes pain in the rectum or perineum, between the scrotum and anus. Patients report that it feels as if there was a golf ball there.” “All traditional treatments are largely ineffective in alleviating Chronic Nonbacterial Prostatitis.” “The effect on a person's life with nonbacterial prostatitis has been liked to the effects of having a heart attack, having chest pain (angina), or active Crohn's disease (bleeding/inflammation of the bowels).”
The severity of this problem is defined in a National Institute of Health document NIDDK Prostate Research Strategic Plan. “Despite it's relatively high prevalence (estimates have ranged from 2.7 to 9.7 percent in men 18 years and older), prostatitis remains a poorly understood disorder and is very challenging to treat. Moreover, prostatitis, specifically in its chronic form CP/CPPS can be physically and psychologically devastating for many patients. For example, the QOL (quality of life) for a patient with chronic prostatitis has been reported to be similar to that experienced by patients with certain forms of heart disease or active Crohn's disease.” “In the case of chronic prostatitis, there is virtually no understanding of the etiology or pathophysiology of disease and there are no prevention strategies or generally effective therapies.”
Given the debilitating nature of Chronic Prostatitis and that it can persist for years or even throughout life, a cushion body that addresses all aspects of sitting discomfort is needed. Patients often find it desirable to sit in a more incline position shifting weight away from the perineum and further back on the ischia and buttocks. This increases pressure on the coccyx and lower sacrum, so an effective means to relieve this pressure is needed.
Persons experiencing rectal or perineal pain and discomfort often seat themselves on a donut-shaped cushion to prevent contact with and pressure on the affected area. Although relatively inexpensive, donut-shaped cushions do not provide a desired degree of relief. For example, in many cases donut-shaped cushions result in tension being exerted in the perineal region. Such tension can cause increased discomfort due to the contour surface pulling or compressing tissue. When centered to alleviate the perineum, donut-shaped cushions can concentrate pressure in the coccyx or genital area. Also, they tend to place the pelvis in abnormal positions making them an undesirable choice for prolonged use.
Another common means to alleviate pressure is a recess or channel along the centerline on the upper surface of the cushion body. This feature alleviates direct pressure along the interior of the pelvis to the extent that it resists deformation. The typical format is a channel formed by a straight line depression or recess. This general approach fails to accommodate to the specific form and function of the pelvic anatomy. It also fails to counter anomalies in pressure created by the underlying surface on which the cushion body is placed.
An alternative means to alleviate pressure is a slot or linear opening that breaches the cushion body. This approach structurally weakens the cushion body. The compressive force of a seated person is highest at the ischial tuberosity. Any opening between the ischia will allow the cushion body to separate and deform. A longer opening provides better accommodation to the user, but it will increase the tendency to separate. In general, a thinner cushion body is desirable, but this will increase separation and deformation.
Most cushion designs fail to account for the surface on which they are placed. When the shape of the cushion is important to its function, a rigid base is typically designed into the cushion body. Wood, plastic and steel are commonly used to form the base in many orthopedic cushion designs. A rigid base will force a specific shape, but it limits the cushion's use. For example, a rigid base is poorly suited to many vehicle seats that are specific in size and are bolstered along the sides. This approach negates many positive attributes found in a well designed seat.
What is needed is a seat cushion that provides effective isolation to the perineal, rectal, and coccyx area. One design requirement is the capability to substantially reduce direct and lateral pressure in the specified area. Another design requirement is the capability to control deformation in the areas between and forward of the ischia. A cushion body should be inexpensive to manufacture and use readily available materials. It should accommodate to a wide variety of every day seating, and provide proper pelvic support. It should function in complement with a well designed seat and not negate advantages.